The ERA-ACT funded Pre-ACT project presents findings from its Work Package 5, demonstrating the workflow developed in the Pre-ACT project demonstrated on case studies from UK, the Netherland and from Norway. The presentation will be divided into three parts.

Part 1: Effect of faults and heterogeneities on CO2 storage, case study from the Smeaheia, offshore Norway

Ane Lothe (SINTEF) will present the Smeaheia area case study, at the Horda Platform, offshore Norway. It is a potential site for CO2 storage with large aquifer sandstone reservoirs in the Middle to Upper Jurassic Sognefjord, Fensfjord and Krossfjord Formations.One of the identified risks in the pre-feasibility study for a site within the Smeaheia region, is the possible effects of regional pressure depletion due to production at the nearby Troll Gas Field. Dynamic reservoir simulation studies, including the Sognefjord formation in the wider Troll Field region, indicate that the pressure at the Smeaheia site could be significantly depleted during the injection period and in the decades following cessation of CO2 injection. The pressure depletion would cause a reduction in the density of the injected CO2 and a corresponding increase in the CO2 volume. Lothe will evaluate two main monitored parameters that could be used to determine whether the storage site is developing towards "safe" containment: 1) pore pressure, and 2) CO2 saturation.

Part 2: Building heterogeneous reservoir realisations using the Endurance structure, UK

Jim White (BGS) will present an overview of the role of geological heterogeneity in CO2 storage.The talk will include a discussion on the analysis of geophysical and subsurface data from the Southern North Sea and the requirement to include these assessments in model construction.After considering the role heterogeneity has played at European CO2 storage sites a range of geological realisations will be assessed for the Endurance structure.Subsequent synthetic down-hole pressure and marine seismic modelling studies will be used to demonstrate how monitoring data could be assessed to quantify conformance at CO2 storage sites.

Part 3: Quantifying monitoring effectiveness of downhole gauges for conformance verification of injection well in depleted gas reservoir systems

In this presentation, Eduardo Barros (TNO) will introduce the problem of designing the instrumentation of wells for CO2 injection in depleted gas reservoirs. Inspired by the feasibility studies for CO2 injection in a reservoir located offshore the Netherlands, a numerical model of the well system was constructed to evaluate a range of operational and injectivity scenarios. Conformance criteria are defined in terms of pressure and temperature bottom-hole conditions in the injection well. Eduardo will show how the Pre-ACT workflow for quantitative conformance verification can be used to determine the expected contribution of different monitoring configurations (i.e., placement of downhole gauges) for accurate probabilistic conformance assessment in this system. We will conclude with a discussion on how this sort of analysis prior to the deployment of sensors can help operators to better design effective monitoring strategies.

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The ACT Pre-ACT project (project no. 271497) has received funding from RCN (Norway), Gassnova (Norway), BEIS (UK), RVO (Netherlands), and BMWi (Germany) and is co-funded by the European Commission under the Horizon 2020 programme (ACT Grant Agreement No 691712). In addition, we like to acknowledge the following industry partners for their contributions: Total, Equinor, Shell, TAQA.